FIG. 6.
LT-NP immunizations protect mice against L. monocytogenes-NP challenge. Groups of BALB/c mice were immunized with 30 pmol of LT-NP once or twice (21 days after the first immunization [D21]) or were not immunized. After 28 days all mice were injected i.v. with 0.73 LD50 of L. monocytogenes-NP. The number of bacteria per spleen was determined 72 h later. The lines indicate the mean numbers of CFU/spleen for the groups. The results are representative of three independent experiments. The asterisk indicates that the P value is <0.01 for a comparison with unimmunized mice.